hLL2 (epratuzumab) is a humanized monoclonal antibody that binds to CD22, a surface antigen expressed exclusively on B-lymphocytes. Clinical studies in patients with B cell lymphomas have shown that epratuzumab is safe and well tolerated across a wide range of doses. Although the exact mechanism is unknown, indirect evidence suggests that the antibody is depleting target B lymphocytes. Epratuzumab is made available by Immunomedics, Inc., and will be used under an investigator (NIH)-initiated IND.